What is Huntington’s disease?

Huntington’s disease (HD) is a disorder affecting nerve cells in the brain. Mild symptoms, which include forgetfulness, clumsiness and personality changes first appear in middle age. Over the next 10-20 years, a person with HD gradually loses all control of their mental and physical abilities. There is no cure for HD at the moment, although some of the symptoms can be treated with drugs.

What causes Huntington’s disease?

The symptoms of Huntington's disease (HD) appear when an abnormal protein builds up in nerve cells in certain areas of the brain, causing the cells to die. One of the brain areas affected is the area that controls movement. Cells in the outer layer of the brain also die, affecting mental abilities. In 1993, researchers discovered that people with HD have a single altered gene, which somehow triggers this process.

Brain scan from a patient with Huntington disease (right) showing a larger cavity where brain cells have died, compared with a normal brain (left).

How is Huntingdon's disease inherited?

Huntington’s disease (HD) is caused by a single altered gene, which is passed on from one generation to the next in affected families. The symptoms of HD usually start to appear in affected people between 30 and 50 years old, but this varies. With one affected parent, each child has a one-in-two chance of inheriting HD. Children who do not carry the altered gene are free from the condition and cannot not pass it on to their own children.

Is there a test for Huntington’s disease?

As the symptoms of Huntington's disease (HD) do not usually appear until middle age, some people only discover they are at risk when one of their parents or grandparents is diagnosed. A genetic test is available to HD families that can tell people whether or not they have inherited the altered gene, but not the age at which they will start to develop symptoms. Although there is no cure available at the moment, genetic tests can help people at risk of HD make decisions about their future. However most decide not to take the test.

DNA analysis of Huntington disease. Each lane shows a different person's DNA: two bands in the normal (N) range show someone is unaffected. One band in the H range predicts the person will get Huntington disease.